A hard disk drive is a non-volatile storage device which stores digitally encoded data on one or more rapidly rotating platters with magnetic surfaces, collectively referred to as the disk. It is known that there is no read-back verification that data was properly written to the disk itself. Therefore, a failure in the write driver (also referred to as a writer output circuit), i.e., the circuit that is responsible for controlling the data that is to be written on the disk via by the write head, will go undetected until the user attempts to retrieve data, at which point the data is lost.
A disk drive preamplifier, which is a circuit used to amplify data before it is written to the disk and typically includes a write driver, sometimes includes a circuit to detect an open write head or a write head shorted to ground. However, such a write head open or short detection circuit does not necessarily detect write driver failures.